Method of treating tobacco smoke to eliminate metal carbonyl content thereof

ABSTRACT

A method is disclosed for determining and introducing the amount of oxygen required to be added to tobacco smoke from conventional smoking devices to deliver a smoke free of metal carbonyls. The required increase in percent oxygen in the smoke depends in part on the content of transition metals in the unsmoked tobacco, and in part on the carbon monoxide content of the tobacco smoke, and is calculated to be equal to the product of the logarithm of the ppm of &#39;&#39;&#39;&#39;iron + cobalt + nickel&#39;&#39;&#39;&#39; and 4 log (percent carbon monoxide in the smoke) divided by a constant. Specifically, the amount of oxygen added is calculated from the formula O- Log M X 4 log% CO/K. wherein O is the increase in the percent oxygen in the smoke, M is the iron, cobalt and nickel content in parts per million in the unsmoked tobacco, % CO is the per cent carbon monoxide in the smoke and K is 3.13 but not exceeding that calculated from this formula wherein K is 1.90.

baited States Patent Staltly [151- 3,656,489 [451 Apr. 18, 1972 [54] METHOD UIF TREATING TOBAiCCU SMUKIE T1) EMMHNATE METAL CARBUNYL UDNTENT THEREOF OTHER PUBLICATIONS R. L. Stedman The Chemical Composition of Tobacco and Tobacco Smoke" Dept of Agriculture Phila. Pa. 19118 Received Oct. 18 1967 p. 153- 207 p. 184 cited Primary Examiner-Melvin D. Rein ArtrneySol B. Wiczer 7] ABSTRACT A method is disclosed for determining and introducing the amount of oxygen required to be added to tobacco smoke from conventional smoking devices to deliver a smoke free of metal carbonyls. The required increase in percent oxygen in, the smoke depends in part on the content of transition metals :in the unsmoked tobacco, and in part on the carbon monoxide content of the tobacco smoke, and is calculated to be equal to the product of the logarithm of the ppm of iron cobalt nickel" and 4 log (percent carbon monoxide in the smoke) divided by a constant.

9 Claims, 4 Drawing Figures \QARETTE A 72 Inventor: Eldon Stahly, 2813 Deirfield Drive, E1

licott City, Md. 21043 [22] Filed: Aug. 26, 1969 [21] Appl.No.: 853,055

Related 111.5. Application Data [63] Continuation in-part of Ser. No. 765,589, Oct. 7,

1968, Pat. No. 3,473,535, which is a continuation-Mnpart of Ser. No. 303,929, Aug. 22, 1963, abandoned.

[52] U.S.Cl ..131/9,131/15,131/17 [51] lint. Cl. ..A241) 15/02 [5 8] Field of Search 1 3 119 1] lfiQ-jfif}, l' [56] References Cited UNITED STATES PATENTS 3,404,687 10/1968 Richards et a1 ..131/B 2,429,567 10/1947 Sowa ..131/ 2,809,637 10/1957 Hale ..131/9 2,981,261 4/1961 Rupert... ....l31/9 2,992,647 7/1961 Figge ..131/9 3,251,368 5/1966 Neurath ..131/15X 3,380,458 4/1968 Tovey et a1. .....l31/17 3,473,535 10/1969 Stahly ..131/9 FOREIGN PATENTS OR APPLICATIONS 876,669 9/1961 Great Britain ..131/9 MICROGRAMS Fei-co-rui" 2o CARBONYLS 1N TOBACCO SMOKE (CIGARETTE a CIGARETTE D 0; DILUTION or TOBACCO SMOKE VOLUME O /VOLUME OF SMOKE OXYGEN DlLUT/ON PATENTEDAPR 18 1972 3, 656,489

CIGARETTE A MICROGRAMS "F. Co +Ni 2o cA RBONYLS g aftg CIGARETTE 0 we CIGA RETTE B o DILUTION OF TOBACCO SMOKE VOLUME o /vowme OF SMOKE OXYGEN D/LUT/ON FIG. 1

POROUS PAPER Eon. AVERAGE AIR. INTRODUCTION To ewe 0.05 VOLUME OXYGEN PER VOLUME OF SMOKE; TOBACCO TREATED WITH UREA PERDXIDE TO SUPPLY 0.0a VOLUME OF SMOKE OXYGEN PER VOLUME 0F SMOKE TOBACCO TREATED WITH SODIUM PERBORATE To RELEASE 0.1.0 VOLUME OXYGEN PER. VOLUME HQ 2 F/G. 4

PUFF BY INTRODUCTION OF AIR. V TOR ELDON E. STAHLY TTOR E Y FIG. 3

METHOD OF ATHNG TOBACCO SMOKE T EMMKNATE METAL C ONYL CONTENT 1 1'11 .1 i

The present invention is a continuation-impart of my copending Ser. No. 765,589 filed Oct. 7, 1968 now U.S. Pat. No. 3,473,535 in turn a continuation-in-part application of Ser. No. 303,929, filed Aug. 22, 1963, and now abandoned, with which it was copending, and relates to a method of improving tobacco smoke by reducing the content of metal carbonyls of .the smoke.

More particularly this invention relates to controlled introduction of air or oxygen into tobacco smoke in smoking devices, e.g., cigarettes, cigars, and pipes, the air or oxygen serving to produce smoke free of metal carbonyls, and pertains to a method of determining the amount of oxygen required for providing a tobacco smoke free of metal carbonyls for tobaccos of different metal contents.

The term metal carbonyls as used herein refers to compounds of a metal and carbon monoxide of the formula Me(CO) where Me is a metal which forms carbonyls such as ferrous metal and x is either 4 or 5 and to compounds containing a metal and CO, and further includes nitrosyl and hydrocarbonyl, wherein the metal-carbonyl combination also contains nitrosyl (NO) and/or hydrocarbonyl (COT-l) groups respectively which may be designated by formula Me(CO),,(NO),,, and Me(CO) (COl-l),

Objects of the invention severally and interdependently are to provide an improved tobacco smoke free of metal carbonyls or their combined nitrosyl or hydrocarbonyl analogues; provide an improved cigarette smoke having reduced contents of metal carbonyl as compared to conventional cigarettes; improved cigar and pipe smoke as compared to conventional cigar and pipe smoke; and improved tobacco formulation which will provide a smoke with a reduced metal carbonyl content; an improved method and tobacco formulation for conventional smoking devices which will provide an improved tobacco smoke. The most prevalent and toxic of the carbonyl derivatives are iron, cobalt and iron, nickel carbonyls; this and other carbonyls being removed by the present invention; and to an improved method and tobacco smoke in which the metal carbonyls are substantially eliminated by introduction of oxygen or of a material which releases oxygen to dilute the tobacco smoke.

In combustion of tobacco in conventional smoking devices, some carbon monoxide is formed. The carbon monoxide content of tobacco smoke has been found to vary from 4 to 11 volume percent, in spite of an apparent sufficiency of air for complete oxidation of CO to C0 The amount of CO present is presumably dependent in part on the ratio of oxygen to tobacco in the combustion zone. The carbon monoxide will not be oxidized further outside of the combustion zone in the absence of a catalyst, and hence is always present in significant amounts in the smoke in unburned portions of the cigarette. I

Metal carbonyl formation is dependent on the reaction of the carbon monoxide with metal compounds or metal complexes present in the tobacco in the cooler unburned portions of the tobacco because iron, cobalt, and nickel carbonyls completely dissociate at 150 to 200 C. Thus these volatile metal carbonyls form behind or below the combustion zone of a cigarette, cigar or pipe at temperatures below 100 C. To demonstrate this formation of metal carbonyls, a gas containing 7 percent carbon monoxide was passed over cigarette tobacco at a temperature of 50 C. and it was found that the nickel content of the tobacco was reduced from 10 micrograms per gram to l microgram per gram, cobalt content from 1.3 micrograms to 0.11 microgram per gram, and iron from 330 to 170 micrograms per gram of tobacco.

Conventional tobacco smoke, more particularly conventional cigarette, cigar, and pipe tobacco smoke, contains substantial traces of metal carbonyls, especially of nickel, cobalt, and iron carbonyls which are removed from the smoke by the invention of U.S. Pat. No. 3,473,535.

It has long been known that such metal carbonyls are highly toxic and dangerous materials even in trace amounts. Sax,

Handbook of Dangerous Materials, published in 1951 by Reinhold Publishing Company, New York, prescribed a maximum allowable concentration of cobalt in the air as 0.4 parts per million, and the Twenty-Second American Conference of Government Hygienists in Apr. 1960 placed the maximal atmospheric concentration of nickel carbonyl for a working day at 1 part per billion (A.M.A. Arch. Environmental Health 1, 140-144, year 1960). Further, carcinogenic aspects of nickel carbonyls have been reported by the Drs. F. W. Sunderman, Sr. and Jr. (American Journal of Clinical Pathology, 35, 203 1961)). Iron carbonyl is also considered to be toxic, although less toxic than nickel and cobalt carbonyls. Accordingly, the cumulative toxicity effects of these three metal carbonyls in tobacco smoke can be expected to be greater than that reported for nickel carbonyl alone. From my examples in the present Cl? and said copending application, it is evident that the quantities of metal carbonyls present in the smoke from conventional cigars, pipes, and plain and filter cigarettes exceed the quantities deemed objectionable by the above authorities. The metal carbonyl content of conventional tobacco smokes depends in part on the metal content of the tobacco.

The invention of Ser. No. 765,589 removes metal carbonyls from tobacco smoke, and thus serves as a safeguard to smokers against exposure to metal carbonyls. By that new process metal carbonyls are removed from tobacco smoke by introducing air laterally through the sidewalls of the smoking device such as cigarette paper and simultaneously enriching the air with oxygen derived from an oxygen-evolving chemical compound such as a peroxy compound which releases oxygen when warmed by the smoke. A combination of the oxygen from the air and from the chemical compound supplies the minimum volume of air or oxygen which 1 found necessary to remove the metal carbonyls from smokes of tobaccos of presently conventional metal contents. The smoke behind the combustion zone in conventional non-filter or filter cigarettes, cigars, or pipes which contains some unused oxygen but requires additional oxygen to produce a smoke entirely free of the carbonyls of iron, cobalt and nickel. The minimum amount of oxygen required is in part dependent on the amount of metals present in the tobacco in the form of salts, complexes or coordination compounds.

I have now discovered that the air dilution required for a specific tobacco to maintain a smoke free of metal carbonyls is dependent in part on (1) the metal content of the unsmoked tobacco, and (2) the carbon monoxide (CO) content of the tobacco smoke. The latter in turn, is dependent on the completeness of oxidation of the organic vapors and of the CO from the tobacco, hence on the tightness of packing of the tobacco in the smoking device. These dependencies thus offer a means of partial control of the metal content of the smoke. I have found a somewhat complex relationship between required oxygen dilution of the smoke, the metal content of the tobacco, and CO content of the smoke. The least amount of oxygen dilution required equals the log of the total iron, cobalt and nickel measured in parts per million in the unsmoked tobacco multiplied by 4 times the log of the percent of the CO in the smoke and divided by the constant 3.13. The oxygen dilution value is thus defined as the increase in 0 concentration in the smoke to deliver metal free smoke. This relationship is represented by the formula:

pound in the cigarette paper, the tobacco, or smoking device: or the oxygen may be obtained by a combination of an (1) oxygen-releasing compound and (2) laterally introduced air.

The procedure employed in demonstrating the present invention was (1) the smoking of a group of 60 cigarettes each of three brands (D, B, and A) to serve as controls. (2) Sixty cigarettes were smoked for each example of oxygen dilution. The method of scrubbing of the smoke and analysis for nickel carbonyl was that used by F.W. Sunderman Sr. and F.W. Sundcrman Jr. (American Journal of Clinical Pathology, 35, 203-9 (1969)) wherein alcoholic iodine solution and nitric acid scrubbers absorbed carbonyls of iron, cobalt, and nickel from the smoke. The metal contents of the scrubbers were determined by colorimetry based on a, a-dipyridyls, dimethyl glyoxime and ethylenediamine tetraacetic acid respectively. These values for metal carbonyl contents of the smoke were confirmed by analyses of tobacco of the unsmoked cigarette, together with the butt tobacco and ashes of the smoked cigarette; when filter cigarettes were tested the filter was analyzed before and after smoking to obtain contents of iron, nickel, and cobalt. These analytical determinations on the tobacco, ashes and filters were made by a combination of chemical and spectrophotometric methods; the latter were similar to the colorimetry above.

The smoking was accomplished by a mechanical smoking system wherein 35 ml puffs" were taken in collecting about 350 ml of smoke for control tests and up to 500 ml or more were collected in the dilution tests utilizing my invention. The 35 ml" were made in a measured manner by use of a bulb which on expansion drew 35 ml of smoke and on compression passed the puff of smoke into the scrubbing system described by Drs. Sunderman (local citation). Further details are given as required in the descriptions of the examples. FIG. 1 shows graphically the relationship between oxygen dilution and metal carbonyl content of tobacco smoke for three brands of conventional cigarettes. The source of oxygen for dilution of the tobacco smoke can be from laterally introduced air alone through pores or holes in the smoking device appropriately placed as in HG. 3, or an oxygen-releasing com pound alone as in FIG. 4 or by a combination of air dilution and an oxygen-releasing compound alone as in FIG. 4 or by a combination of air dilution and an oxygen-releasing compound as exemplified in H6. 2. Possible deviations result from the limiting degrees of accuracy of the analytical methods of determining the pertinent components of tobacco smoke. The errors are within about i 4 percent, and to assure elimination of metal carbonyls from tobacco smoke the calculated oxygen dilution is increased by adjusting K to obviate possible low values calculated for the dilution. Thus K 3.13

As background for the present invention data are presented in Table l to demonstrate how the required amount of oxygen is experimentally determined to produce a metal-free smoke. These data are plotted in FIG. 1.

TABLE 1 Variations in metal contents of tobacco require provision of different minimum amounts of oxygen dilution to eliminate the metal carbonyls from the tobacco smoke. My present invention provides a method of determining the minimum oxygen dilution of the tobacco smoke which will produce a smoke free of all metal carbonyls. The dilution with oxygen is effected by introduction of air into the smoking device or by introduction of oxygen via an oxygen-releasing compound as disclosed in Ser. No. 765,589 filed on Oct. 7, 1968, or by a combination of air and an oxygen-releasing compound. The smoking device can be a cigar, cigarette or pipe.

Oxygen in controlled amounts in introduced into the tobacco smoke behind the combustion zone of the tobacco. The oxygen is introduced in an amount sufiicient to eliminate the metal carbonyls. The mechanism of elimination can be destruction of metal carbonyls already formed, or prevention of formation of the carbonyls by the excess oxygen. By which mechanism the elimination is effected is immaterial for the practice of my invention since the invention resides in substantial elimination of the metal carbonyls in the tobacco smoke by use of oxygen. Using my invention cigarette manufacturers can determine the required minimum dilution to guarantee the absence of metal carbonyls in the tobacco smoke from their smoking devices. Further, it has been discovered that to avoid loss of flavor the maximum oxygen dilution can be established by use of a second equation:

log M 4 (log C) T 25 wherein O, M and C are defined as hereinbefore and K 1.90.

Selectively sized introduction of oxygen in cigarettes, cigars, or pipes is effected in one of three ways:

a. by providing openings of controlled area in the smoking device, e.g. in a pipe or in the cigarettes. These openings are placed from 10 to 20 mm. in front of the present conventional filters of cigarettes or pipes, or for non-filter cigarettes, from 10 to 20 mm. from the mouth of the cigarette, the mouth end being the end which enters the smokers mouth, thus introducing a constant amount of oxygen (via air) with each puff.

b. by incorporating into the tobacco formulation a compound which releases oxygen into the smoke as it is warmed to the range of to 200 C.

c. by a combination of (a) and (b).

Each provision, (a), (b), and (c) reduces the metal carbonyls in the smoke by a mechanism as discussed above.

The use of a uniformly porous paper alone is not successful for maintaining the required low metal carbonyl content of the smoke, because if porosity is properly adjusted for the full unsmoked cigarette there is not sufficient oxygen (introduced as air) in the partly smoked cigarette to maintain sufiiciently low metal carbonyl content in the cigarette smoke.

Micrograms of metal" car- Oxygen addition (via air) bonyls in smoke (tot. Fe,

Increase Co, Ni From a gram of in O2 0:, CO, OA/CO, tobacco ol. Os/vol. cone, Mole Mole Mole ratio smoke b percent percent percent. (approx) D B A 0.0/1.0 11.4 7. 0(-. 2) 1. 5 273 100 300 t 1.1 1; 5 6.1 2. 0 183 233 2. 0 13. 1 5. 1 2. 6 68 0 2. 5 13. 9 5. 0 2. S 0 0 0 3. 8 15. 2 3. 9 3. 9 0 O 0 4. 3 15. 7 3. 5 4. 5 0 0 0 Increns n 0: at. point of zero m ct nl carbonyl in smoke O (2. 3) (20) (2. 2%)

n Microgrums of metals of D, B, and A.

per gram of tobacco are 341, 125, and 317 respectively for cigarettes the oxygen.

=1"rom Fro. 1.

Of course a large excess of oxygen can be introduced, e.g. with cigars and cigarettes, by use of a high porosity paper or high. porosity outer leaves, but smoking pleasure is correspondingly reduced as the oxygen dilution is increased up to 0.2 volume oxygen per volume of smoke. For the tobaccos of Table l at least an increase in concentration in the smoke of 2 percent is provided to ensure metal free smoke; and for pleasure, not more than 0.12 volume of oxygen per 1.0 volume of smoke should be provided by my invention to give an increase in oxygen concentration of 3.2 percent when dilution is provided via oxygen-releasing additives, via air introduction, or by a combination of air and oxygen-releasing additive.

The oxygen-releasing additives disclosed in Ser. No. 765,589 and which may be used as a source of oxygen in practicing the present invention, must not deleteriously affect the tobacco or the tobacco smoke. They can be applied to the cigarette paper, to the outer cigar leaves, or to the tobacco of cigarettes, cigars or pipes. Examples of useful additives are shown in Table 2, amounts of additive are shown as calculated necessary to release ml 0 which is sufficient oxygen to dilute the tobacco smoke to produce metal-free smoke for the five cigarette brands G, A, B, D, and F.

. 6 smoked after providing perforations 20 mm. from the mouth" end of the tobacco for both filter and nonfilter cigarettes so that 0.04 volume oxygen was introduced per volume of smoke and the oxygen concentration was 12.8 vol. percent in the diluted smoke. Similar smoking experiments were performed for each brand of cigarettes to obtain data for oxygen dilution of 0.06 volume per volume of smoke (l3.4 vol. percent oxygen); also data were obtained for about 0.1 volume oxygen introduced per volume of smoke l4.2 percent oxygen in smoke); and finally for a dilution of 0.2 volume of oxygen per volume of smoke 15.7 mole percent oxygen in the diluted smoke). Analyses for Fe, Ni and Co contents of the butt tobacco ashes, filters and smoke were obtained; and the carbon monoxide of the smoke was determined. The metal contents at the various oxygen dilutions were plotted for each brand of cigarette in charts similar to that of FIG. 1. it was discovered that minimum oxygen dilutions required to provide a metal carbonyl free smoke conform to a formula. This said fonnuia permits calculation of the minimum oxygen concentration, hence the oxygen addition required to attain a metalfree smoke provided the CO content of the smoke and also the metal contents (Fe, Co, and Ni) of the tobacco are known Lrnetal-free smoke signifying zero content of iron, cobalt and TABLE 2 [Oxygen Releasing Additives of this Invention] Weight Tempera- Grarns to percent Melting ture C.) produce 15 available point, for 02 Additive ml. oxygen oxygen C. releases Sodium perborate:

Monohydrate 0. 14

Trihydrate O. 2 Lithium pcrborate 0. 1 Sodium phosphate poroxyhydrata O. 22 Ammonium perborate- 0.1 Sodium peroxydiphosphate(NaiPzOs) 0. Urea peroxide 0.12 Potassium superoxide .c 0.06 Sodium carbonate peroxyhydrate 0.15 Potassium peroxydicarbonate(KzCzOe) 0. 13 Sodium peroxymon0carbonate(Na2CO4) A 0.16 Tertiary butyl hydropcroxide 0.13 16 Liquid 1 Ca 100 and higher. Releases oxygen upon contact with C0, 002, or H1O.

EXAMPLE 1 The tobacco of five brands of cigarettes were sampled and analyzed as follows: From each of 10 cartons of each brand, one pack of cigarettes was selected; and for each brand, from each of the 10 packs selected, three cigarettes were taken and dismantled, and the tobacco therefrom was combined and analyzed for iron, nickel, and cobalt. Then from each of said selected packs six cigarettes were smoked leaving about 30 percent of the tobacco as unsmoked butt tobacco. The butt tobacco, ashes, and smoke from each set of 30 cigarettes were analyzed and the amounts of iron, cobalt and nickel determined for each phase. Also the average carbon monoxide content (CO) of the smoke was determined. These smoking tests were repeated with 60 more cigarettes of each brand using six cigarettes selected from each pack taken--from 10 aforesaid cartons of each brand of cigarettes-but the repeat test was made with small perforations 20 mm. from the filter for each filter cigarette and 20 mm. from the mouth end of the nonfilter cigarettes so that air was introduced to give 0.02 vol. oxygen/vol. smoke, and i2.l vol. percent oxygen in the smoke.

Then 60 cigarettes of each brand were selected from l0 packs; (one pack from each of the said 10 cartons) and were Log p.p.m. of (Fe+Co+Ni)i,'4 log ()0) Oxygen dilution K wherein ppm of (Fe Ni Co) parts per million of the sum of the contents of the three metals in the tobacco, CO percent of carbon monoxide (log 10% CO 1.0), oxygen dilution is the increase in 0 concentration required for metal-free smoke, and K 3.13.

TABLE 3 [Oxygen dilution required to attain tobacco smoke free of metal carbonyis] G D A B F None None Total 406. 0 340. 8 316. 6 125. 3 85. 1 Log of p. .m. metal carbonyls 2. 51 2. 5 2. 5 2.10 1. 93 Percent O in smoke 6. 0 5. 8 5. 6 5.8 5. 9 Oxy en addition (vol. oxygen/ vo ume smoke) for meta free smoke 0. 077 0. 074 0. 072 0. 052 0. 055 Percent 02 in smoke after ()2 addition 13. 9 13. 7 13. 6 13.4 13. a Increase in 02 concentration by On addition 2. 4 2. 8 2. 2 2.0 1. i1

i log percent CO (b diiu.

Average K Thus the invention provides a metal-freetobacco smoke when log M X 4 log C/K wherein O, M and C are as defined hereinbefore and K 3.13. The use of 3.13 obviates effects of analytical deviation and gives a margin of safety so that a metal-free smoke is assured. To exemplify the use of my formula, for a tobacco containing 100 ppm of (Fe Co Ni), and packed in a cigarette (Brand J) so that burning produces 5.9 percent CO in the smoke, it is calculated that a minimum oxygen concentration of 13.4 percent, or addition of air to afford O /vol. of smoke, is required to give a metal-free smoke A value of K of 3.13 is used to offset possible variations in metal analyses. 0 2%. The concentration 0 of the smoke must be increased from 11.4 to 13.4 percent.

EXAMPLE 2 To exemplify further the value of the formula of Example 1, i.e., log ppm of(Fe +Co Ni) (4 log% CO)/3.l3 minimum concentration increase in oxygen required for metal-free smoke for a tobacco containing 20 ppm of the combined metals, and which is packed in a filter cigarette, Brand H, to produce a smoke containing 1 1 percent of CO, we calculated the minimum increase in oxygen concentration to be required is 3.0 percent. This requires addition of 0.1 volume of oxygen per volume of smoke when 0 is supplied via air addition. To test the validity of the calculation the following experiments were perfomted:

Sixty cigarettes of Brand H were selected; six each of packs of the same carton, and they were smoked with the mechanical smoker after three perforations were made about 0.8 inch from the mouth end of the cigarette. Each perforation was about 39 mils in diameter and sufiicient to give 0.10 volume of oxygen per volume of smoke while smoking only 50 percent of the cigarette-Le. half the length. The smoke was completely metal-free, as predicted for the oxygen dilution of 0.10 per volume ofsmoke.

A set of 60 cigarettes then were selected, six from each of the same 10 packs of Brand H used in the smoking tests just performed, and these were perforated with two holes per cigarette 45 mils in diameter and 0.8 inches from the mouth end. These perforations were previously found to give an oxygen dilution of 0.092 volume of oxygen per volume of smoke, which was less than the value 0.098 volume calculated just preceding. These 60 cigarettes when smoked in the mechanical smoker were found to give an average smoke of 9 ppb of iron, cobalt, and nickel carbonyls." These results exemplify the fact that the control formula of my invention is operative.

EXAMPLE 3 Similar smoking tests were performed with Brand J cigarettes described hereinbefore which had 102 ppm of (iron cobalt nickel), and it was demonstrated that the calculated increase on 0 content of 2 percent in the smoke required 0.062 volume oxygen addition via air for metalfree smoke, and this amount did in fact give metal-free smoke whereas 0.048 vol. of oxygen per volume of smoke gave a smoke having 5 ppb (parts per billion) of the metal carbonyls.

EXAMPLE 4 Experiments were performed with oxygen-releasing chemicals. Sixty cigarettes of each Brand G, D, A, B, and F were selected for these tests. The cigarettes were impregnated with the amount of sodium perborate calculated to release the required amount of oxygen to produce metal-free tobacco smoke. lmpregnation was accomplished by dipping the cigarettes in sodium perborate solution and drying at 65 C., and repeating the operation until the desired amount of sodium perborate monohydrate (0.14 g) was impregnated in each cigarette (determined by weight increase and confirmed by analysis of six cigarettes of each brand impregnated). Table 4 shows the data calculated. Mechanical smoking experiments gave metal-free smoke, thus demonstrating the usefulness of my invention to determine the required increase in percent 0 calculated equal to log M X 4 log (%CO)/K.

TABLE 4 [Increase in oxygen concentration 1gp]; oxygen releasing compound Cigarette G D A B F Na perborate, g 0. 13 0. 126 0.121 0. 103 0. 098 (Fe+Co-l-Ni) p.p.m. in

tobacco 406. 0 340. 8 316. 0 125. 3 85. 1 Percent 02 in smoke alter 'lution 13. 9 13. 7 13.6 13. 4 13. 3 Percent CO in smoke 6.0 5.0 5.6 6 8 5. 9 0: addition 0. 029 0. 027 0. 026 0. 022 0. 027 "Log percent CO 0.78 0.76 0.76 0.76 0.77 4 log percent 00 3.12 3. 0t 3. 00 3.01 3. 08 0* (increase in percent O2) 2. t3 2. 45 2.4 2.0 1. 9

Percent increase in oxygen is calculated as follows:

(G) 0 log p.p.m. (Fe+Co+N1)X4log% CO 2.61X3.12

2153x301 (D) O= 3. When K=3.13 increase in percent 0: is calculated adequately high (clillable 3).

EXAMPLE 5 EXAMPLE 6 Cigarettes were made by using a do-it-yourselt" cigarette making mach'me. A cigarette tobacco was used which contained 101 ppm (total) of iron plus cobalt plus nickel." Sixty cigarettes were prepared with conventional cigarette paper. These were designated Brand K. Sixty were then prepared with cigarette papers the insides of which were impregnated with lithium perborate (Li B0 by spraying with an aqueous solution, and drying, so that each cigarette had 0.08 g of Li B0 These were designated Brand L. The Brand K cigarettes were smoked mechanically as described hereinbefore, and analyses of the smoke showed 7.0 percent carbon monoxide, 11.9 percent oxygen and 105 ppb of metal carbonyls. It was calculated by my formula 10g 101 4 log C that an increase of 2.2 percent oxygen in the smoke was required to eliminate the metal carbonyls therefrom. The Li BO content would supply 12.5 ml 0 per cigarette (at 32 C.), i.e., per 500 ml smoke, or an increase of 2. 1 mole percent.

Therefore a hole about 0.5 mm. in diameter was punched approximately 2 cm from the mouth end of each of Brand L cigarettes. This hole size was determined to supply 0.2 ml oxygen (1 ml air) per ml smoke and in combination with the 2.1 mole percent 0 from the Li B0 the total in 2.2 percent increase in oxygen content was attained in the smoke in comparison with Brand K smoke. When 59 of Brand L cigarettes were smoked the analysis of the smoke showed 14.1% 0,, 6.7% CO and zero metal carbonyl content. Thus the oxygen content was increased from 11.9 for Brand K to 14.1 percent.

0 (increase in 0 This example confirms the value of my formula in calculating the required oxygen dilutions for elimination of metal carbonyls from the tobacco smoke.

EXAMPLE 7 Preparation of coated cigarette paper of Example was repeated except that each cigarette had 001 g of Li B0 and 1.5 ml of oxygen was released per 500 ml smoke; were smoked and analysis of the smoke showed 12.2 percent oxygen. Three holes about 1 mm. in diameter were punched in each of the remaining 30 cigarettes approximately 2 cm from the mouth end. The size of the holes were calculated to introduce sufficient air to increase the oxygen content of the smoke from 12.2 percent to 14.1 percent. Analysis of the smoke from these 30 cigarettes confirmed the fact that the smoke contained from 14.0 to 14.2 percent (avg. 14.1 percent) oxygen and further that no metal carbonyls were present in the smoke (vs 6 ppm with no air addition).

EXAMPLE 8 Twelve cigars of Brand S were smoked as controls using the mechanical smoker. The cigar tobacco showed a combined content of 292 ppm of Fe Co Ni"; the smoke contained 6.5% CO, and 80 ppb metal carbonyls. The minimum increase in oxygen concentration required for a metal-free smoke was calculated to be 2.6 percent by using my formula and the value for K 3.13 as determined in Example 1 (i.e. 3.27 minus the deviation of 0.14). The calculation was as follows for the cigars: log 292 X 6 .5/3.13 2.6%.

Twelve cigars of the same brand S were wrapped with leaf wrappers which had been sprayed on the inside with a solution of sodium monoperoxycarbonate and dried to give a coating of 0.16 g of the peroxy compound which was calculated to give an increase of 0.2 percent oxygen in the cigar smoke. Then three holes l mm. in diameter were made in the outer layer 3 cm from the mouth end of the ciga so that an oxygen increase of 2.4 percent (0.137 volume air/volume of smoke) was obtained during smoking. These 12 cigars were then smoked mechanically. The oxygen from the peroxycarbonate (0.002 vol/volume of smoke) plus the oxygen introduced laterally through the holes in the wrapper leaf (0.024 vol. per volume of smoke) equalled 0.026 total, the same as the above calculated minimum increase in oxygen concentration or dilution. The smoke was free of metal carbonyls. Thus when the cigars are modified according to my invention to give at least the calculated increase in oxygen concentration or dilution of the smoke a tobacco smoke is provided which is free of metal carbonyls.

While there have been described herein what are at present considered to be preferred embodiments of the invention, it will be obvious to those skilled in the art that modifications and changes may be made without departing form the essence of the invention. Other oxygen releasing compounds such as silicate peroxyhydrates, alkali metal perborosilicates and any other such non-toxic compounds may be used. Thus any desired means of introducing oxygen into the tobacco smoke following the combustion zone and prior to entering the smoker may be used, it being considered desirable to pass the air-diluted smoke through a filter section of filter material other than tobacco to remove oxides, hydroxides or other residues or reaction products of the iron, nickel, and cobalt carbonyl with oxygen. The type of smoking device-cigar, cigarette or pipe-is'immaterial with respect to the practice of my invention. The type of filter material is non-critical and any otherwise acceptable conventionally used filter material such as cellulose esters, cellulose itself, alkyl celluloses, polystyrene, activated carbon, silica, silicates, alumina and the like may be used. It is therefore to be understood that the exemplary embodiments are illustrative and not restrictive of the invention, the scope of which is defined in the appended claims, and that all modifications that come within the meaning and range of equivalency of the claims are intended to be included therein.

lclaim:

II. In the smoking of tobacco in conventional smoking devices, the method of providing a tobacco smoke free of metal carbonyls which comprises introducing an amount of oxygen into the tobacco smoke sufficient to increase the oxygen content of the smoke by an amount at least equal to the value calculated from the formula 0 Log M X 4 log %CO/l(, wherein O is increase in percent oxygen in the smoke, M is the iron, cobalt and nickel content in parts per million in the unsmoked tobacco, %CO is the percent carbon monoxide in the smoke, and K is 3.13, but not exceeding that calculated from the same formula wherein K is 1.90.

2. 1n the smoking of cigarettes, the method of providing a tobacco smoke free of metal carbonyls which comprises introducing an amount of oxygen laterally into the tobacco smoke by way of small holes distributed through the cigarette paper controlled in size and number sufficient to increase the oxygen content of the smoke by an amount at least equal to the value calculated from the formula 0 bog M X 4 log %CO/K, wherein O is increase in percent oxygen in the tobacco smoke, M is the iron, cobalt and nickel content in parts per million in the unsmoked tobacco, %CO is the percent of carbon monoxide in the smoke, and K is 3.13, but not exceeding that calculated from the same formula wherein K is 1.90.

3. The method of claim 1 wherein the oxygen is introduced laterally via air additions into the smoking device through small holes.

4. The method of claim 2 wherein the oxygen is introduced both laterally via small holes in the cigarette paper and from an oxygen-releasin com ound in the bumable charge, the total oxygen bemg t e sai total quantity of oxygen introduced from both sources.

5. The method of claim 1 wherein the oxygen is introduced by incorporation of an oxygen-releasing non-toxic peroxy compound in the bumable charge of the smoking device.

6. The method of claim 5 wherein the oxygen-releasing compound is selected from the group consisting of perborates, peroxides, silicate peroxyhydrates, perborsilicates, and percarbonates of alkali forming metals and ammonium, tertiary butyl hydro peroxide and urea peroxides.

7. The method of claim 11 wherein the oxygen introduced comprises a combination of oxygen from air introduced through holes and oxygen from an oxygen-releasing compound incorporated in the bumable charge to the smoking device.

8. The method of claim 11 wherein the smoking device is introduced via an oxygen-releasing compound coated on the inside of the cigarette paper.

9. The method of claim 7 wherein the smoking device is a cigarette and the oxygen-releasing compound is incorporated by coating on the inside of the cigarette paper. 

2. In the smoking of cigarettes, the method of providing a tobacco smoke free of metal carbonyls which comprises introducing an amount of oxygen laterally into the tobacco smoke by way of small holes distributed through the cigarette paper controlled in size and number sufficient to increase the oxygen content of the smoke by an amount at least equal to the value calculated from the formula O Log M X 4 log %CO/K, wherein O is increase in percent oxygen in the tobacco smoke, M is the iron, cobalt and nickel content in parts per million in the unsmoked tobacco, %CO is the percent of carbon monoxide in the smoke, and K is 3.13, but not exceeding that calculated from the same formula wherein K is 1.90.
 3. The method of claim 1 wherein the oxygen is introduced laterally via air additions into the smoking device through small holes.
 4. The method of claim 2 wherein the oxygen is introduced both laterally via small holes in the cigarette paper and from an oxygen-releasing compound in the burnable charge, the total oxygen being the said total quantity of oxygen introduced from both sources.
 5. The method of claim 1 wherein the oxygen is introduced by incorporation of an oxygen-releasing non-toxic peroxy compound in the burnable charge of the smoking device.
 6. The method of claim 5 wherein the oxygen-releasing compound is selected from the group consisting of perborates, peroxides, silicate peroxyhydrates, perborsilicates, and percarbonates of alkali forming metals and ammonium, tertiary butyl hydro peroxide and urea peroxides.
 7. The method of claim 1 wherein the oxygen introduced comprises a combination of oxygen from air introduced through holes and oxygen from an oxygen-releasing compound incorporated in the burnable charge to the smoking device.
 8. The method of claim 1 wherein the smoking device is introduced via an oxygen-releasing compound coated on the inside of the cigarette paper.
 9. The method of claim 7 wherein the smoking device is a cigarette and the oxygen-releasing compound is incorporated by coating on the inside of the cigarette paper. 